Cant get paypal API settings to work in garage sale

I listed a number of cars on ebay using garage sale. Many have ended but buyers can pay paypal. Garage sale said to update API information from paypal which I did. When I test paypal connection popup says security header incorrect. Cant find any reference on paypal-ebay or garage sale to security header. HELP!!

Hi Gary,

you only need to enter your PP credentials if you want to monitor your PayPal accounts for incoming payments.

Otherwise you only need to enter your PP email address.

Regards, Kristian